Electrical attachment plug



JNL 6, 1948- P. E. GuRlN 2,434,154

ELECTRICAL ATTACHMENT PLUG Filed oct. 1e, 194e v INVENTOR @n .5. Gaf/N.

Patented Jan. 6, 1948 UNITED STATES PATENT OFFICE ELECTRICAL ATTACHMENT PLUG y Paul E. Gnrin, Brooklyn, N. Y. Application October 16, 1946, Serial No. 703,631

The present invention relates. to electrical attachment plugs and, more particularly, to the type commonly known as male connectors having one or more terminal prongs extending therefrom to be received in a recess or recesses in a female receptacle connector to make electrical contact with suitable contact means in the latter.

A general vobject of the presentfinvention is to provide such an electrical male attachment, plug which is of simple and economical construction that meets with lire underwriters requirements and which, in mounting to a female receptacle, may be so manipulated as to move 'laterally prong structure thereof for temporarily locking the male plug to the female receptacle in an efcient manner, while assuring that after said mountation any pull upon the electrical cord or conductors connected thereto will tend to maintain or increase the locking action effectively to avoid accidental detachment.

A more specific object of the invention is to provide such an electrical locking male attachment plug characterized by at least one pair of metallic contact '.lngers, together serving as a terminal prong and which may be laterally spread apart for temporary locking in a receptacle recess, the plug including a pair of body members, one of which carries the cooperating pair of metallic contact ilngers serving as a prong and the other carrying a camming structure, whereby when one of the two'body members are moved relative to each other in an axial direction the camming structure will tend to spread the contact fingers laterally apart and to maintain them in such spread-apart relation for secure locking in the receptacle recess; the plug being provided with one or more electrical conductor anchorages so that a pull thereon, which may occur accidentally as a result of a person tripping over the conductor extending between the plug and an electrical appliance, will tend to maintain or increase the locking function of the spread-apart contact flngers thereby effectively avoiding accidental detachment, while permitting ready detachment of the plug by simple movement of the body members relative to each other in the direction opposite to that which accomplishes the locking.

Another object of the present invention is to provide such an electrical male attachment plug, which is featured by a cup-shaped shell of lnsulating material in which is slidably received a circular base plate of insulating material with the latter equipped with at least one pair of cci--` s claims. (ci. 11s-'361) operating contact ngers to serve as a terminal prong, the shell carrying a camming finger juxtaposed to the contact fingers whereby upon movement of the base plate down intothe shell the camming finger williA cause the contact ngers to belspread apart at their outward free ends for temporary locking in a receptacle recess, the base eiectively carrying an electrical conductor lanchorage for electrical contact with prong contact linger structure whereby when the electrical conductor or wire is fastened to the anchorage and extends out through a hole in the shell a pull on the conductor or wire will cause the cammlng means on thel shell to spread the,A contact fingers laterally apart to lock them in a receptacle recess, or, after being so mounted and temporarily locked in position, such pull will eiliciently tend to maintain or increase such locking action.

A further object of the present invention is to provide structural embodiments. of the device which are readily constructed and permit ecient use and operation thereof.

Other objects 'of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combination of elements and arrangement of Y parts, which will be exemplied in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

Fig. 1 is an enlarged top plan View, with parts broken away, of an embodiment of the electrical locking male attachment plug of the present iny vention;

Fig. 2 is a transverse section taken substan- I tially on line 2-2 of Fig. l, showing conductor wires, parts of which are broken away, connected thereto;

Fig; 3 is a view similar to Fig. 2 taken substantially on line 3--3 of Fig. 1, with the parts in their initial position prior to manipulation for accomplishing locking action;

Fig. 4 is a view similar to Fig. 3, indicating in dotted lines parts ofl a typical female receptacle, with parts of the male plug shown manipulated to locking positions# Fig. 5 is an enlarged perspective view of one of therefrom that the preferred embodiment of the present invention comprisesa cup-shaped shell I0 of insulating material having an axial hole II in the back or bottom thereof through which a connecting cord or electrical conductors or wires may extend. The shell I0 slidably receives therein a disc or circular base plate member I2 of suitable insulating material, which preferably is notched in the edge thereof, such as at diametrically opposed points I3, I3, slidably to receive guide iins I4, I4 extending axially and arranged on the inner wall of the shell.

The base plate I2 has a pair of laterally spacedapart rectangular apertures I5, I5, each of which receives therethrough a terminal prong structure or assembly I6 of metal having good electrical conductivity. Each terminal prong assembly I6 preferably comprises a -pair ofresilient metallic contact iingers I1 and I8, with each having a laterally extending footing I9 adapted to be seated against the back face of the base plate I2 and anchored together to the base plate by means of a rivet 2|. Each footing I9 is preferably provided with an ear 22 having a threaded hole 23 therein threadably to receive together a terminal anchorage screw 24 for the usual purpose. As shown in the drawing, each of the two terminal screws 24, 24 connects an insulated conductor or wire 25 to one of the pair of terminal prongs I6, I6, and those conductors or wires extend from out of the shell through the axial hole II.

Of each pair of contact fingers I1 and I8, together constituting va terminal prong I6, one thereof, for example, contact finger I1, has an elongated slot 26 extending longitudinally thereof from the footing I9 to an outer end at 21 there to provide an oblique camming face facing rearwardly, as shown in Figs. 3, 4 and 5. The cooperating contact finger I8 has a similar slot 23 also terminating at its outward end in an oblique camming face 29 facing rearwardly and sloped in the opposite direction. The contact finger I8 preferably is provided with a stop bar 30 extending transversely of slot 28, for a purpose to be explained later. Preferably the footing I9 of finger I8 is provided with a conductor anchoring hook 3l to take the strain of! of terminal screw 24.

The shell I Il carries therein a pair of laterally spaced-apart, axially extending, camming lingers 32 fixed to the shell preferably during the molding of the latter. Each camming finger 32 is slidably received by the cooperating slots 26 and 28 of each prong structure I6, and the head end ofthe camming finger is preferably provided with a laterally extending nose 33 adapted to engage beyond the transversely extending stop bar 30 on contact finger I8. The head end of each camming finger 32 is provided with a pair of forwardly facing oblique camming faces 34 and 35 adapted to cooperate with the rearwardly facing oblique camming faces 21 and 29 of the spring fingers I1 and I8. If desired, one or more of the cooperating camming surfaces on iingers I1, I 3 and 32 may be roughened to minimize too ready sliding action that may at times tend to an unwanted demountation of parts under certain conditions.

The spring fingers I1 and I8 are preferably made from resilient metallic material of good electrical conductivity and, although in the embodiment shown in Figs. 1 to 7, inclusive, the camming fingers 32 may be formed of material other than metal of good electrical conductivity, such as hard rubber, they are. for purposes of manufacturing economy and simplicity, made of metal.

In assembling the parts, the camming fingers 32, 32, xed in the' shell III, are slidably received in the elongated slots 26, 26 of the contact fingers I1, I1 with their noses 33, 33 snapped into the apertures intervening the oblique camming surfaces 29, 29 and the cross bar stops 36, 36 of the spring fingers I 8, I8.- T'hus the cross bars 36. 38 serve to limit outward movement of the prong structures I6, I6 relative to the camming lingers 32, 32. If the unit is marketed in assembled condition the purchaser can readily demount the parts for anchorage of conductors to the prong assemblies I6, I6 by ilexing the fingers I8, I8 inwardly and withdrawing camming fingers 32, 32 with shell I0 from the prong assemblies and plate I2. After the conductors 25, 25 are anchored to base plate I2 and connected to screws 24, 24, the parts are reassembled in the above manner'. This assembled structure with the base plate I2 loosely and slidably received in the' top of the cup-shaped shell I0 is then ready for use in the usual manner and constitutes a structure similar to that shown in Fig. 3.

In operation the attachment plug of the present invention is to be associated with a female receptacle and, as shown in Fig. 4 by way of example, the female rceptacle may be of typical construction, as indicated in dotted lines at 36, comprising a pair of recesses 31, 31 having terminal contacts 38, 38 therein. In those recesses 31, 31 the prong structures I8, I6 are received in the usual manner and, without manipulation of the plug structure for purposes of temporarily locking it to the receptacle, the inner spring iingers I8, I8 of the pair of prongs I6, I8 make face contact with the receptacle contacts 38, 38 in the'usual manner. However, as desired, the male attachment plug of the present invention is preferably temporarily locked to the female re.

ceptacle by holding the shell I0 in xed position and pulling on the conductors 25, 25 in the direction of the arrow in Fig. 4. As a result, the

oblique camming surfaces 34 and 35 of each of.

the camming fingers 32, 32 are caused to slide along the oblique camming surfaces 21 and 29 of spring fingers I1 and I8 with rearward movement of the latter as the base plate I2 is pulled down into the shell III. As a result,y the free ends of the resilient spring fingers I1 and I8 of each prong assembly I6 are spread or sprung apart, as shown in Fig. 4, to lock the prong structure I 6, I6 in the recesses 31, 31 of the female receptacle 36. This spreading or springing action of each of the pairs of spring fingers I1 and I8 is permitted without interference by the cam-v ming iingers 32, 32 due to the provisions of the slots 26 and 28 in the spring fingers. It will be understood, of course, that slot 28 may be omitted from the spring finger I8 if the parts are carefully made and fitted together, so long as the aperture for the spring finger nose 33 is provided.

securely locked in the However. it has been found that for commercial production it is preferable to slot both of the spring fingers I1 and I8 longitudinally from their footings I9, I9 for considerable extent and to provide the vaperture adjacent the camming surfaces 29 of spring finger I8 by the transverse stop bar 30.

As previously remarked, the male attachment plug of the present invention may be employed in the usual manner of use of, common types of male attachment plugs without manipulation for temporary locking, since the prong assemblies I6, I6 in their initial conditions, when inserted in female receptacle recesses, make electrical contact with contact members in the recesses in the usual manner. The contact members of common .types of female receptacles, such as that indicated f in dotted lines in Fig.

4, are usually made from relatively thin sheet metal springiness to assure good electrical contact with relatively stiff male prongs. Accordingly, the springing apart of the pair of contact iingers I'I and I8, which together form each prong aassembly I6 of the present structure, by the camming operation of the camming finger 32 is readily permitted in a. manner resulting in lateral deviation of the free end of the contactfinger I8 as well as that of i1, due to the resilient springiness of the contact member in the female receptacle recess. Of course it will be understood that should some special type of female receptacle be employed,` where the contact members therein are relatively stii so as to reduce camming deviation of the contact fingers I8, I8, the temporary locking action will be permitted by greater deviations of the free ends of the contact ngers I'I, I1, when the camming fingers 32, 32 are thrust inwardly relative to the contact `fingers I1, I8 and I1, I8, or vice versa.

With the male plug attachment of the present invention temporarily locked to the female receptacle,\as shown in Fig. 4, it will readily be seen that any accidental tug or pull on the conductors 25, 25 will, instead of tending to detach the male plug, merely maintain or tend to increase the locking action. Thus, for example, in household use where conductor cords usually extend between female wall receptacles near the baseboard to oor lamps and other appliances with parts thereof lying on the floor, if one should trip over the cord or engage cleaning operations, the male plug will remain female receptacle. However, the structure provides for ready detachmentv of the male plug at will. If the shell I is grasped in the fingers and drawn out away from the female receptacle, the. camming fingers 32, 32 will slide out relative to the pairs of Contact fingers and have considerable l through whichis received the electrical conductors 2B. each anchored by the screw 24 to a spoolsupported footing 43 of a camming finger 44 slidably received between the pair of contact spring ngers 40, 48. The latter preferably have at their outer ends outwardly facing oblique camming faces 45, 45 against which rearwardly facing cammingV surfaces 46, 46 of an enlarged spearhead-shaped outer end of camming finger 44 seat.

Accordingly, when such a male plug structure is applied to a female receptacle in the usual manner, if the shell Ill is held fixed a tug on the conductors 25 will cause the spool 4I to slide rearwardly in the shell causing camming finger oblique surfaces 46, 46 to slide against oblique camming surfaces 45, 45 of contact lingers 48, 40 to spring them apart to locking position.

It will be noted that in the structure of Fig. 8 the conductors 25 are'anchored toand in electrical contact with the camming ngers l44 rather than with the contact ngers 40, 40. Accordingly those camming ngers 44 are preferably made from metal of good electrical conductivity so as to assure electrical connection between the con-l ductors 25 and the contact members in the female receptacle recesses, via camming fingers 44 and at least one of each pair of contact fingers 40, 40. If desired, the contact ngers 40, of each pair thereof may be provided with opposed I :notches 41,- 41 on shown, into which opposed corners of the spearhead'of the camming finger 4 4 may snap when ythe structure is manipulated to locked position.l

Since `a portion of the spool 4I extends out through the axial hole II of the shell I0, the male plug structure of Fig. 8 may be readily detached by pushing inward on the back end of the spool so as to return the camming fingers 44 to it accidentally during I'I and I8 permitting the latter, due to their resiliency, to return to their original positions ming iingers eventually engaging the stop bars so, en thereafter to withdraw with the'shen In the prong structures I6, I5 and their supporting base plate I2. i

Similar functions may be embodied in the male attachment plug structures of modified form as shown in Fig. 8. For example, the shell I0 may have iitted to it a face plate 39 on which may be mounted a cooperating pair of laterally spacedapart Vmetallic spring fingers 40, 40 received through a hole in the plate 39 and preferably anchoredto the back face of the latter. The shell I0 may slidably receive therein a spool 4I of insulating material having a central bore 42 the position shown in Fig, 8. Y

It will thus be seen that the objects set forth 'above, among uothers made apparent from the preceding description, are elciently attained and, since certain changes may be made in the above construction and different embodiments of the invention could be made without departing rom the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the `invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

.1. An electrical locking male attachment plug comprising, in combination, a pair of body members of insulating material movable relative to each other in an axial direction, a terminal prong carried by one of said body r'nembers and extending out from the front side thereof in an axial direction for insertion into a receptacle recess, said prong comprising a pair of metallic contact finger means adapted to be spread laterally apart for temporary locking in the receptacle recess, a metallic camming finger means mounted on the other of said bodyv members juxtaposed to said contact nger means, anchorage means on one of said body members for fastening thereto an electrical conductor adapted to make electrical contact with the metallic finger means thereon, and an oblique camming face on the latter of said metallic finger means facing the inner faces thereof, as

toward the rear of its supporting body member whereby pull on an electrical conductor anchored thereto will spread and tend to keep spread said contact finger means in locking position with relative axial movement of said body members.

2. An electrical locking male attachment plug comprising. in combination, a pair of body members of insulating material movable relative to each other in an axial direction, a terminal prong carried by one 'of said body members and extending out from the front side thereof in an axial direction for insertion into a receptacle recess, said prong comprising a pair of metallic contact ngers adapted to be spread apart for temporary locking in the receptacle recess'. a camming finger mounted on the other of said body members juxtaposed to said contact fingers, anchorage means on thefirst-mentioned body member for fastening thereto an electrical conductor adapted to make electrical contact with at least one of said Contact fingers, and cooperating camming surfaces on at least one of said contact fingers and said `camming finger whereby pull on an electrical conductor fastened to said anchorage will tend to move said contact fingers and said camming finger longitudinally relative to each other to spread and tend to keep spread the former in locking position.

3. An electrical locking male attachment plug comprising, in combination, a pair of body members of insulating material movable relative to each other in an axial direction, a terminal prong carried by one ofsaid body members and extending out from the front side thereof in an axial direction for insertion into a receptacle recess, said prong comprising a pair of resillent metallic contact fingers adapted to be spread apart for temporary locking in 'the receptacle recess, a pair of oblique camming faces on said fingers facing rearwardly and sloped in opposite directions, a camming finger mounted on the other of said body members juxtaposed to said contact fingers and having a pair of forwardly facing oblique camming faces for cooperation with those of said contact fingers to spread the latter apart when they are moved rearwardly with respect to said camming finger, and an anchorage on the first-mentioned body member for fastenf ing thereto an electrical conductor adapted to make electrical contact with at least one of sand contact fingers whereby pull on an electrical conductor fastened to said anchorage will tend to move said contact fingers rearward relative to said camming finger.

4. An electrical locking male attachment plug comprising, in combination, a cup-shaped shell of insulating material having a conductor outlet hole therein, a circular base of insulating material slidably received in 4-said shell for rela-l tive axial movement, a' terminal prong mounted on said base and extending outl from the front side thereof in an axial direction for insertion into a receptacle recess, said prong comprising a pair of resilient metallic contact fingers adapted to be sprung apart for temporary locking in the receptacle recess, a. pair of oblique camming faces on said fingers facing rearwardly and sloped in opposite directions, a camming finger mounted on said shell juxtaposed to said contact fingers and having a pair of forwardly facing oblique camming faces for cooperation with those of said contact fingers to spring the latter apart when they are moved rearwardly with respect to said camming finger, and an anchorage on the back side of said base for fastening thereto an electrical conductor adapted to make electrical contact with at least one of said contact fingers whereby pull on a terminal conductor fastened to said anchorage and extending out through the he1e in seid sneu wm tend to move said base down into said shell and said contact fingers rearward relative to said camming finger.

5. An electrical locking male attachment plug comprising, in combination, a pair of body members of insulating material movable relative to each other in an axial direction, a terminal prong carried by one of said body members and extending out from the front side thereof in an axial direction for insertion into a receptacle recess, said prong comprising a pair of resilient metallic contact fingers adapted to be sprung apart for temporary locking in the receptacle recess, both of said contact fingers being longitudinally slotted with the outer ends of the slots providing a pair of oblique camming faces facing rearwardly and sloped in opposite directions, a camming finger mounted on the vother said body members and slidablyreceived in at least one of the slots of said contact fingers, said camming finger having on its outer end a pair of forwardly facing oblique camming faces for cooperation with those of said contact fingers to spring the latter apart when they are moved rearwardly with respect to said camming finger, and an anchorage on the first-mentioned body member for fastening thereto an electrical conductor adapted to make electrical contact with at least one of said contact fingers whereby pull on a terminal conductor fastened to said anchorage will tend to move said contact fingers rearward relative to said camming finger.

6. An electrical locking male attachment plug comprising, in combination, a cup-shaped shell of insulating material having an axial outlet hole therein, a circular base of insulating material slidably received in said shell, a pair of laterally spaced-apart terminal prongs mounted on said base and extending out from the'front side thereof in an axial direction for insertion into receptacle recesses, each of said prongs comprising apair of resilient metallic contact fingers fixed to said base so that their outer free ends may be divergingly spread apart for temporary locking in one of the receptacle recesses, each of said contact fingers being longitudinally slotted and having an oblique camming face at the outer end of said slot with the two oblique camming faces of each of said pair of contact fingers facing rearwardly and sloped in opposite directions, transversely extending abutment means foreshortening the slot of one of said contact fingers of each pair thereof to provide a withdrawal-limiting stop, a pair of laterally spaced-apart camming fingers fixed in said shell and extending axially out of the same each being slidably received through said base and in the elongated slot of one contact finger of a pair thereof with its head end having a laterally extending nose received beyond said stop of the companion contact finger of that pair to limit axial movement of said base out of the shell, each of said camming Afingers being provided on its head end with a pair of forwardly facing oblique camming faces for cooperation with those of said contact fingers to spring the latter apart when they are mo'ved rearwardly with respect to said camming finger with movement of said base down into said shell, and a pair of anchorages on said base each for fastening thereto an electrcal conductor adapted to make electrical contact with one of said pair of contact ingers PAL E. GURIN.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name Date Cornwell Nov. 4, 1941 Shearer June 18, 1935 Thorin. July 28, 1936 

